The present invention relates to a sheet collecting apparatus for collecting and collating sheets carried out of an image formation apparatus such as a copier and printer, and more particularly, to improvements in a sheet collation collection mechanism.
Generally, a collecting apparatus for collating sheets carried out of an image formation apparatus, etc. is widely used as a post-processing apparatus, for example. Then, in this structure, a level difference is formed on the downstream side of a sheet discharge outlet to provide a collection tray, and a sheet is carried out to above the tray by a sheet discharge roller of the sheet discharge outlet, and is thereby piled and stored upward sequentially.
For example, an apparatus is disclosed in Japanese Unexamined Patent Publication No. 2006-008384 (Patent Document 1) in which sheets with images formed by an image formation apparatus are collated and collected on a processing tray, and this bunch of sheets is stapled in the center, and then folded in a magazine finish. In the Document, a sheet from the image formation apparatus is carried into inside a path disposed in the vertical direction, a sheet discharge roller is disposed in the path, a level difference is formed on the downstream side of the roller, and a collection tray is disposed therein. Then, disposed further are a stapling unit for stitching a bunch of sheets collected on the collection tray and a folding unit for folding in magazine form.
In such a sheet collation apparatus, consideration must be given to maintain the page order between a sheet that is carried in from the sheet discharge outlet and already collected sheets. This is because when the rear end of the prior sheet is curled and raised in carrying a subsequent sheet onto collected prior sheets from the sheet discharge outlet, the subsequent sheet sinks below the prior sheet, and the pages get out of order.
Therefore, not shown as a Cited Document, such a sheet discharge mechanism has conventionally been used frequently that a sufficient level difference is formed between the sheet discharge outlet and the collection tray, and that even when the rear end of the collected prior sheet is curled upward, the subsequent sheet is caused to enter from above and dropped. In such a sheet discharge structure, since a large level difference is provided between the sheet discharge outlet and the tray, there is a problem that the apparatus becomes large in size.
Then, in the apparatus described in Patent Document 1, the collection tray is inclined in the direction in which the sheet from the sheet discharge outlet is curled so as to prevent the subsequent sheet from breaking in. The page order is reserved by thus curling the sheet in the opposite direction to the curl resulting in incorrect collating, but the pages may get out of order due to the extent of curl of the collected prior sheet or curl of the front end of the carry-in sheet.
Further, in an apparatus described in Japanese Unexamined Patent Publication No. H09-118468 (Patent Document 2), a guide member rotating in paddle form is provided between the sheet discharge outlet and the collection tray, and the page order is reserved by rotating the guide member whenever a sheet enters from the sheet discharge outlet. In other words, the mechanism is proposed that when the sheet front end enters from the sheet discharge outlet, the guide member is positioned above the piled sheets, guides carry-in of the sheet, and after the sheet is carried in, turns to return onto the uppermost sheet.
Similarly, in an apparatus described in Japanese Unexamined Patent Publication No. 2008-297060 (Patent Document 3), a turning guide member is provided between the sheet discharge outlet and the collection tray, and is turned whenever a sheet enters. Further, not shown as a Cited Document, to resolve out of page order as described above, another apparatus is known where a sheet that is carried in the collection tray is switched back, the sheet rear end is backed toward the back side of the sheet discharge outlet, and the page order is thereby reserved.
In the sheet collation collection apparatuses as described above, there is the problem that the pages get out of order by a carry-in sheet sinking in between collected sheets when the sheet that is carried out of the sheet discharge outlet is loaded and stored. Therefore, conventionally, a level difference (drop) formed between the sheet discharge outlet and the collection tray is formed to the extent that the front end of the carried-out sheet does not reach the rear end of collected sheets. Therefore, since a drop of several tens of centimeters is required as a level difference between the sheet discharge outlet and the tray on the downstream side of the outlet, upsizing of the apparatus is inevitable.
Further, to miniaturize the apparatus, it is attempted to dispose the paddle-shape guide member in the rear end portion of the collection tray, but speedup of the apparatus is significantly affected by turning the guide member 180 degrees or 360 degrees at intervals of sheets that are sequentially carried out.
Furthermore, similarly, it is proposed to switch back the sheet that is carried in the collection tray to back the sheet rear end, but moving back and forth every time the sheet that is successively carried out becomes a problem in the high-speed processing.
Therefore, the inventor of the invention reached the idea of providing a guide member in stairs form at the sheet-discharge-outlet end of the collection tray, and using the guide member, preventing a sheet from rising, while guiding the front end of the carry-in sheet.
It is a main object of the invention to construct, in a simplified structure, a sheet collecting apparatus that is compact and that enables sheets successively carried out of the sheet discharge outlet to be reliably collated and collected in the order of pages.